TINSLEY Mortimer may finally be getting her dream. The oft-photographed socialite has been filming a reality show with Andrew Glassman, the producer behind “Average Joe” and “Three Wishes” on NBC and “National Bingo Night” and “The Ex- Wives Club” on ABC, sources say. Several weeks ago, just be fore she and her publicity-shy husband, Topper, separated, Tinsley reportedly brought a seven-person camera crew to the couple’s Upper East Side co-op. A rep for Glassman declined to comment.